border-1px($color)
    position relative
    &:after
        display block
        position absolute
        left 0
        bottom 0
        width 100%
        border 1px solid $color
        content ' '
border-none()
    &:after
        display none

bg-image($url)
    background-image url($url+'@2x.png')
    @media (-webkit-min-device-pixel-ratio: 3),(-webkit-min-device-pixel-ratio: 3)
        background-image url($url+'@3x.png')

